---
title: "Vulnerabilities"
description: "1 posts about Vulnerabilities, summarised, each linking to the original."
---

# Vulnerabilities
> 1 posts about Vulnerabilities, summarised, each linking to the original.

## Articles

### [How Cloudflare addressed a cross-tenant data exposure vulnerability in Containers](https://yomu.fyi/post/how-cloudflare-addressed-a-cross-tenant-data-exposure-vulnerability-in.md)
- Company: [Cloudflare](https://yomu.fyi/company/cloudflare.md)
- Author: Hrushikesh Deshpande
- Published: Sep 24, 2026
- Type: Incident / postmortem

Security researcher Oren Yomtov reported a vulnerability in Cloudflare Containers and Sandboxes through the bug bounty program, demonstrating that a Workers Paid account could recover residual disk blocks from previous containers on the same host. The issue arose from Linux device mapper thin provisioning with skip\_block\_zeroing enabled, which left unzeroed 64 KiB blocks when a 4 KiB write triggered allocation, allowing the remaining 60 KiB to retain prior data. Researchers recovered directory structures, database pages, and structurally complete SQLite databases from 18 of 24 placements across four continents, using ext4 checksums to distinguish foreign blocks. Cloudflare removed skip\_block\_zeroing, retired all running container disks, and cleared cached image snapshots created before the mitigation, completing cleanup by September 19. Retained disk-I/O telemetry showed no evidence of malicious exploitation, and the researchers confirmed secure deletion of recovered data.